Developer transport device, developing device, visible image forming device and image forming apparatus

ABSTRACT

A developer transport device includes: a developer containing room for containing a developer; a developer transport member disposed in the developer containing room, the developer transport member transporting the developer in a developer transport direction; and a developer damming member disposed in the developer containing room over the developer transport member, the developer damming member damming up the developer located above the developer transport member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC §119 fromJapanese Patent Application No. 2006-339623 filed Dec. 18, 2006.

BACKGROUND

(i) Technical Field

The present invention relates to a developer transport device, adeveloping device, a visible image forming device, and an image formingapparatus.

(ii) Related Art

In an image forming apparatus in the related art, such aselectrophotographic copiers and printers, image formation is performedin such a manner that a developer holding body is opposed to aphotoreceptor body on whose surface a latent image is formed and thelatent image is visualized with a developer that is carried by thesurface of the developer holding body.

For example, a two-component developer containing a toner and a carrieris used as the developer. The two-component developer is agitated untilit is transported to the developer holding body, whereby lumps of tonerare broken up and the tuner and the carrier are charged throughfriction.

The developer is consumed by image formation and hence requires supply.Furthermore, the developer holding body and the photoreceptor body aredeteriorated as they are used, and hence need to be replaced when theyhave been used for a certain length of time. Therefore, in the imageforming apparatus, a developer supply container (what is called a tonercartridge) is made replaceable (detachable) to supply only a developer,the developing device and the photoreceptor body are made replaceable,or the developer supply container and the developing device areintegrated with each other so as to be replaced together. These measuresare employed widely. In general, such a replaceable developing device issealed so as to prevent the developer from leaking during storage ortransport. When used, such a replaceable developing device is unsealedso as to be rendered usable by causing the developer to flow into thedeveloping device.

SUMMARY

According to an aspect of the invention, there is provided an developertransport device comprising:

a developer containing room for containing a developer;

a developer transport member disposed in the developer containing room,the developer transport member transporting the developer in a developertransport direction; and

a developer damming member disposed in the developer containing roomover the developer transport member, the developer damming memberdamming up the developer located above the developer transport member.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described in detail basedon the following figures, wherein:

FIG. 1 illustrates the whole of an image forming apparatus according toa first exemplary embodiment of the present invention;

FIG. 2 illustrates the image forming apparatus according to the firstembodiment of the invention in a state that an open/close unit isopened.

FIGS. 3A and 3B illustrate a visible image forming device as anexemplary detachable body according to the first embodiment of theinvention; FIG. 3A illustrates a state that it is in use, and FIG. 3Billustrates a state before opening of an initial developer containingroom;

FIG. 4 is a sectional view taken along line IV-IV in FIG. 3;

FIGS. 5A and 5B illustrate a developer transport member and a developerdamming member according to the first embodiment of the invention; FIG.5A is a side view and FIG. 5B is a sectional view illustrating animportant part;

FIGS. 6A and 6B are views as viewed from the direction of arrow VIA inFIG. 5A; FIG. 6A illustrates a state that the developer damming memberis held at a contained position, and FIG. 6B illustrates a state thatthe developer damming member is removed;

FIGS. 7A and 7B illustrate the developer damming member according to thefirst embodiment of the invention; FIG. 7A is a front view and FIG. 7Bis a view as viewed from the direction of arrow VIIB in FIG. 7A;

FIG. 8 is a graph in which the horizontal axis represents the timeelapsed from the start of toner supply and the vertical axis representsthe toner density, and illustrates an experiment of the firstembodiment;

FIGS. 9A and 9B illustrate a developer damming member according to asecond exemplary embodiment of the invention; FIGS. 9A and 9B are afront view and a side view corresponding to FIGS. 7A and 7B of the firstembodiment, respectively; and

FIG. 10 illustrates a developer damming member according to a thirdexemplary embodiment of the invention; FIGS. 10A and 10B are a side viewand a front view corresponding to FIGS. 5A and 7A of the firstembodiment, respectively.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention (hereinafter referred toas embodiments) will be hereinafter described with reference to thedrawings. However, the invention is not limited to the followingembodiments.

To facilitate the understanding of the following description, in thedrawings, the X-axis direction, the Y-axis direction, and the Z-axisdirection are defined as the front-rear direction, the right-leftdirection, and the top-bottom direction, respectively. And thedirections (sides) indicated by arrows X, −X, Y, −Y, Z, and −Z aredefined as the front direction (side), the rear direction (side), theright direction (side), the left direction (side), the top direction(side), and the bottom direction (side), respectively.

In the drawings, the mark that “•” is enclosed by a circle means anarrow that is directed from the back side to the front side of the papersurface and the mark that “x” is enclosed by a circle means an arrowthat is directed from the front side to the back side of the papersurface.

To facilitate the understanding of descriptions which will be made withreference to the drawings, members that are not necessary for thedescriptions will be omitted where appropriate.

Embodiment 1

FIG. 1 illustrates the whole of an image forming apparatus according toa first exemplary embodiment of the present invention.

FIG. 2 illustrates the image forming apparatus according to the firstembodiment of the invention in a state that an open/close unit isopened.

As shown in FIG. 1, in a printer U as an exemplary image formingapparatus according to the first embodiment of the invention, a sheetsupply tray TR1 which contains recording media S as exemplary media onwhich images will be recorded occupies a lower portion of the printer Uand a sheet ejection unit TRh includes a top surface of the printer U. Amanipulation unit UI is disposed at a top position of the printer U.

As shown in FIGS. 1 and 2, the printer U according to the firstembodiment has an image forming apparatus main body U1 and an open/closeunit U2 which can be opened and closed about a rotation shaft U2 a whichare located at the bottom-right corner of the image forming apparatusmain body U1. The open/close unit U2 is configured so as to be movablebetween an open position (indicated by solid lines in FIG. 2) forexposing the inside of the image forming apparatus main body U1 toenable supply of a developer, replacement of a member in failure, orremoval of a jammed recording medium S and a closed position (indicatedby two-dot chain lines in FIGS. 1 and 2) where the open/close unit U2 isheld in an ordinary state in which an image forming operation isperformed.

The printer U has a control section C′ which performs various controlson the printer U, an image processing section GS whose operation iscontrolled by the control section C, an image writing device drivecircuit DL, a power device E, etc. The power device E applies voltagesto charging rollers DRy-CRk as exemplary chargers (described later),developing rollers G1 y-G1 k as exemplary developer holding bodies,transfer rollers T1 y-T1 k as exemplary transfer devices, etc. (thesecomponents will be described later).

The image processing section GS converts print information that is inputfrom an external image information transmitting apparatus or the likeinto pieces of latent image forming image information corresponding toimages of four colors of K (black), Y (yellow), M (magenta), and C(cyan), and outputs the pieces of image information to the image writingdevice drive circuit DL with prescribed timing. The image writing devicedrive circuit DL outputs drive signals to a latent image writing deviceROS according to the received pieces of image information of therespective colors. According to the drive signals, the latent imagewriting device ROS emits laser beams Ly, Lm, Lc, and Lk as exemplaryimage writing light beams of the respective colors.

As shown in FIG. 1, visible image forming devices UY, UM, UC, and UK forforming toner images as exemplary visible images of the respectivecolors of Y, M, C, and K are disposed on the right (+Y direction) of thelatent image writing device ROS.

FIGS. 3A and 3B illustrate one visible image forming device as anexemplary detachable body according to the first embodiment of theinvention. FIG. 3A illustrates a state that it is in use, and FIG. 3Billustrates a state before opening of an initial developer containingroom.

As shown in FIGS. 3A and 3B, the visible image forming device UK of K(black) has a photoreceptor body Pk as an exemplary rotary image holdingbody. A charging roll CRk as an exemplary charger, a developing deviceGk for developing a latent image on the surface of the photoreceptorbody Pk into a visible image, a charge removing member Jk for removingcharge from the surface of the photoreceptor body Pk, a photoreceptorbody cleaner CLk as an exemplary image holding body cleaner for removingdeveloper remaining on the surface of the photoreceptor body Pk, etc.are disposed around the photoreceptor body Pk.

After the surface of the photoreceptor body Pk is charged up uniformlyas a result of charging by the charging roll CRk at a charging region Q1k which is opposed to the charging roll CRk, a latent image is writtento the photoreceptor body Pk at a latent image forming region Q2 k witha laser beam Lk. The thus-written latent image is visualized at adevelopment region Qgk which is opposed to the developing device Gk.

The visible image forming device UK of black according to the firstembodiment is a detachable body (what is called a process cartridge) inwhich the photoreceptor body Pk, the charger CRk, the developing deviceGk, the charge removing member Jk, the photoreceptor body cleaner CLk, adeveloper supply container (11+16+18), etc. are integrated together. Asshown in FIG. 2, the visible image forming device UK is configured so asto be able to be attached to and detached from the image formingapparatus main body U1 in a state that the open/close unit U2 is movedto the open position.

Like the visible image forming device UK of black, the visible imageforming devices UY, UM, and UC of the other colors are detachable bodies(what is called process cartridges) which can be attached to anddetached from the image forming apparatus main body U1.

As shown in FIGS. 1 and 2, a belt module BM as an exemplary recordingmedium transport device supported by the open/close unit U2 is disposedon the right of the photoreceptor bodies Py-Pk. The belt module BM has amedium transport belt B as an exemplary recording medium holdingtransport member, a belt drive roll Rd as an exemplary drive memberwhich supports the medium transport belt B, belt support rolls (Rd+Rj)as an exemplary holding transport member support system including afollower roll Rj as a follower member, transfer rolls T1 y, T1 m, T1 c,and T1 k as exemplary transfer devices which are opposed to therespective photoreceptor bodies Py-Pk, an image density sensor SN1 as anexemplary image density detecting member, a belt cleaner CLb as anexemplary holding transport member cleaner, and a medium absorbing rollRk as an exemplary recording medium absorbing member which is opposed tothe follower roll Rj and absorbs a recording medium S on the mediumtransport belt B. The medium transport belt B is rotatably supported bythe belt support rolls (Rd+Rj). The image density sensor SN1 detects,with prescribed timing, the density of a density detection image (whatis called a patch image) which is formed by an image density adjustingmeans (not shown) of the control section C. The image density adjustingmeans performs an image density adjustment or correction (what is calleda process control) by adjusting the voltages applied to the chargersCRy-CRk, the developing devices Gy-Gk, and the transfer rolls T1 y-T1 kand the intensities of latent image writing light beams Ly-Lk on thebasis of the image density detected by the image density detectingmember.

A recording sheet S is taken by a sheet feed member Rp from the sheetsupply tray TR1 which is located below the medium transport belt B, andis transported to a recording medium transport path SH.

In the recording medium transport path SH, the recording medium S istransported by medium transport rolls Ra as exemplary recording mediumtransport members and thereby sent to registration rolls Rr as exemplarysheet supply timing adjusting members. The registration rolls Rrtransport, with prescribed timing, the recording medium S to a recordingmedium absorbing position (region) Q6 where the follower roll Rj and themedium absorbing roll Rk are opposed to each other. The recording mediumS that has been transported to the recording medium absorbing positionQ6 is electrostatically absorbed on the medium transport belt B.

Where a recording medium S is supplied from a manual feed unit TRO, arecording medium S supplied through manual feed members Rp1 istransported to the registration rolls Rr by medium transport rolls Raand then transported to the medium transport belt B.

The recording medium S which is absorbed on the medium transport belt Bpasses transfer regions Q3 y, Q3 m, Q3 c, and Q3 k in order where themedium transport belt B is in contact with the photoreceptor bodiesPy-Pk, respectively.

At each of the transfer regions Q3 y, Q3 m, Q3 c, and Q3 k, a transfervoltage whose polarity is opposite to the toner charging polarity isapplied, with prescribed timing, to the transfer roll T1 y, T1 m, T1 c,or T1 k from the power device E which is controlled by the controlsection C.

In the case of forming a multi-color image, toner images on therespective photoreceptor bodies Py-Pk are transferred in superimpositionto the recording medium S placed on the medium transport belt B by thetransfer rolls T1 y, T1 m, T1 c, and T1 k. In the case of forming asingle-color image (monochrome image), only a toner image of K (black)is formed on the photoreceptor body Pk and transferred to the recordingmedium S by the transfer device T1 k.

After charges are removed from the surfaces of the photoreceptor bodiesPy-Pk by the charge removing members Jy-Jk at charge removing regionsQjy-Qjk, toner remaining on the surfaces of the photoreceptor bodiesPy-Pk is collected by the photoreceptor body cleaners CLy-CLk atcleaning regions Q4 y-Q4 k to clean the surfaces. Then, the surfaces ofthe photoreceptor bodies Py-Pk are charged up again by the chargingrolls CRy-CRk.

The recording medium S to which the toner images have been transferredare subjected fusing at a fusing region Q5 where a heating roll Fh and apressure roll Fp as exemplary heating fusing members of a fusing deviceF are in pressure contact with each other. The recording medium S onwhich the image has been fused is guided by a guide roller Rgk as anexemplary guide member and ejected to the medium ejection unit TRh as anexemplary medium ejection member through ejection rollers Rh.

After separation of the recording medium S, the medium transport belt Bis cleaned by the belt cleaner CLb.

In the case of double-sided printing, the ejection rollers Rh are drivenso as to be rotated reversely and the recording medium S is transportedto a medium flipping path SH2 by means of a switching member GT1. Therecording medium S is sent to the registration rolls Rr again in aflipped state.

In the first embodiment, the fusing device F, the lower ejection roll(drive roll) Rh, the switching member GT1, and the lower guide surfaceof the medium flipping path SH2 constitute an integrated, replaceablefusing device (what is called a fusing unit U3). The upper ejection roll(follower member) Rh is supported by the open/close unit U2.

(Visible Image Forming Device)

FIG. 4 is a sectional view taken along line IV-IV in FIGS. 3A and 3B.

The visible image forming devices UY-UK will be described below indetail. Since the visible image forming devices UY-UK of the respectivecolors are configured in the same manner, only the visible image formingdevice UK of black will be described, that is, descriptions of the othervisible image forming devices UY, UM, and UC will be omitted.

As shown in FIGS. 3A and 3B and 4, the visible image forming device UKis configured in such a manner that a developing unit Uk1 having thephotoreceptor body Pk and the developing device Gk and a cleaning andcharging unit Uk2 having the charging roll CRk, the photoreceptor bodycleaner CLk, and the charge removing roll Jk are assembled. A writinglight passage Uk3 through which a laser beam Lk is to pass is formedbetween the developing unit Uk1 and the cleaning and charging unit Uk2.

The developing unit Uk1 has a developer container 1 which contains adeveloper. The developer container 1 has a lower developer containermain body 1 a, a lid member 1 b which closes the developer containermain body 1 a from above, and a central partition member 1 c which formsa developer transport room (described later) by partitioning thedeveloper container main body 1 a at a central position in theright-left direction.

The developer container 1 has a developer holding body containing room 2which supports the developing roll G1 k as an exemplary developerholding body which is opposed to the photoreceptor body Pk, a firstagitation transport room 3 which is adjacent to the developer holdingbody containing room 2 from the left side and contains a developer, anda second agitation transport room 4 which is adjacent to the firstagitation transport room 3 from the left side. A layer thicknessrestricting member Sk for restricting the layer thickness (i.e., thethickness of developer carried by the surface of the developing roll G1k) is disposed in the developer holding body containing room 2 so as tobe opposed to the developing roll G1 k.

The first agitation transport room 3 and the second agitation transportroom 4 as an exemplary developer containing room are separated from eachother by a partition wall 6. The first agitation transport room 3 andthe second agitation transport room 4 are configured so that developercan move between them at both ends in the front-rear direction.

A two-component developer containing a toner and a carrier is containedas the developer in the developer container 1 according to the firstembodiment. The developer holding body containing room 2, the firstagitation transport room 3, and the second agitation transport room 4constitute the developer containing room (2-4).

As shown in FIG. 4, a toner density sensor SN2 as an exemplary developerdensity detecting member is disposed at the rear end of the firstagitation transport room 3, that is, at the upstream end in thedeveloper transport direction, to detect a toner/carrier mixing ratio(what is called a toner density).

Agitation transfer members 7 and 8 as exemplary developer transportmembers for transporting developer in opposite directions whileagitating it are disposed in the first agitation transport room 3 andthe second agitation transport room 4, respectively. The agitationtransport members (augers) 7 and 8 according to the first embodiment arecomposed of rotary shafts 7 a and 8 a and spiral transport blades 7 band 8 b which are fixedly supported by the rotary shafts 7 a and 8 a,respectively.

As for the agitation transport members 7 and 8 according to the firstembodiment, the diameter of the rotary shafts 7 a and 8 a is 4 mm, thespiral diameter (i.e., the outer diameter of the transport blades 7 band 8 b) is 8 mm, the pitch which is the axial advancement per rotationof the transport blades 7 b and 8 b is 15 mm, and the rotation speed isset at 408.39 rpm. These values may be changed arbitrarily according tothe design.

FIGS. 5A and 5B illustrate the developer transport member 8 and adeveloper damming member according to the first embodiment of theinvention. FIG. 5A is a side view and FIG. 5B is a sectional viewillustrating an important part.

FIGS. 6A and 6B are views as viewed from the direction of arrow VIA inFIG. 5A. FIG. 6A illustrates a state that the developer dammming memberis held at a contained position, and FIG. 6B illustrates a state thatthe developer damming member is removed.

FIGS. 7A and 7B illustrate the developer damming member according to thefirst embodiment of the invention. FIG. 7A is a front view and FIG. 7Bis a view as viewed from the direction of arrow VIIB in FIG. 7A.

As shown in FIGS. 3A and 3B, the lid member 1 b is formed with aninitial developer containing room 9 which is located over the secondagitation transport room 4. As indicated by a broken line in FIG. 4, anopening 9 a extending in the front-rear direction is formed at the lowerend of the initial developer containing room 9. As shown in FIG. 4, thedeveloper damming member 10 is disposed at a rear position of theinitial developer containing room 9 (i.e., at a downstream position inthe developer transport direction of the second agitation transport room4) and is supported rotatably.

As shown in FIGS. 5-7, the developer damming member 10 has a plate-likedamming member main body 10 a and rotation shafts 10 b which project inthe right-left direction and are supported by the damming member mainbody 10 a at positions close to its top. As shown in FIGS. 3A and 7A,the lower portion of the damming member main body 10 a is formed with anagitation member surrounding portion 10 c having a semicircular shapethat conforms to the rotation locus of the transport blades 7 b and 8 bof the agitation transport members 7 and 8. That is, as shown in FIG.5B, the agitation member surrounding portion 10 c according to the firstembodiment is formed to prevent developer from being transported alongthe wedge-shaped space between the second agitation transport member 8and the second agitation transport room 4 (i.e., the shoulder portionsabove the second agitation transport member 8; indicated by a brokenline in FIG. 5B) if the agitation member surrounding portion 10 c is notprovided.

The rotation shafts 10 b of the developer damming member 10 arerotatably supported by a pair of (i.e., right and left) damming membersupport holes 9 b as exemplary damming member support portions which areformed in the initial developer containing room 9 so as to be adjacentto the opening 9 a, whereby the developer damming member 10 is supportedso as to be able to swing between a damming position (indicated by asolid line in FIG. 5A) in the second agitation transport room 4 and acontained position (indicated by a broken line in FIG. 5A) in theinitial developer containing room 9

As shown in FIGS. 5A and 5B, the developer damming member 10 accordingto the first embodiment is held at the damming position by its ownweight. At the damming position, the developer damming member 10 isinclined so as to be come closer to the developer transport member asthe position goes downstream in the developer transport direction. Atthe damming position, the angle θ formed by the damming member main body10 a and the rotary shaft 8 a of the developer transport member (i.e.,horizontal plane) is set an acute angle 60°. This angle may be changedarbitrarily according to the design etc.

In the first embodiment, it may be possible to dispose the rotationshafts 10 b of the damming member 10 in the second agitation transportroom 4. However, as the visible image forming device UK is made smaller(i.e., made thinner in the height direction), the interval between afilm seal FS (described later) as a partition member/opening blockingmember and the developer transport member becomes smaller and hence itbecomes more difficult to secure, in the second agitation transport room4, a space in which to dispose the rotation shafts 10 b. In view ofthis, in the first embodiment, the rotation shafts 10 b are disposed inthe initial developer containing room 9.

A cylindrical developer transport room 11 is formed on the left of thesecond agitation transport room 4. A developer supply mouth 11 a isformed at a position close to the front end of the developer transportroom 11 so as to allow the developer transport room 11 to communicatewith the second agitation transport room 4, and a developer inflow mouth11 b is formed at a position close to the rear end of the developertransport room 11. A developer supply member 12 for transporting thedeveloper in the developer transport room 11 toward the developer supplymouth 11 a is disposed in the developer transport room 11.

As for the developer supply member 12 according to the first embodiment,the diameter of a rotary shafts 12 a is 4 mm, the spiral diameter (i.e.,the outer diameter of a transport blade 12 b) is 8 mm, the pitch whichis the axial advancement per rotation of the transport blade 12 b is 8mm, and the rotation speed is set at 100 rpm. These values may bechanged arbitrarily according to the design.

A first developer supply room 16 is formed on the left of the developertransport room 11, and a second developer supply room 18 which isconnected to the first developer supply room 16 via developer droppassages 17 which are formed at both ends in the front-rear direction isdisposed over the first developer supply room 16. A first developertransport member (developer supply member) 21 and a second developertransport member (developer supply member) 22 for transporting thedeveloper in the first developer supply room 16 toward the developerinflow mouth 11 b are disposed in the first developer supply room 16.

The first developer transport member 21 has a rotary shaft 21 a and atransport thin-film member 21 b which is a flexible resin thin-film madeof PET (polyethylene terephthalate) or the like and is supported by therotary shaft 21 a. The transport thin-film member 21 b is formed withcuts 21 c which are inclined from the axial direction, and an auxiliarythin-film 23 for increasing the strength and thereby allowing thedeveloper to flow toward the developer inflow mouth 11 b more easily isstuck to the transport thin-film member 21 b at such a position as to beopposed to the developer inflow mouth 11 b. Therefore, while the firstdeveloper transport member 21 is rotating, the developer is transportedtoward the developer inflow mouth 11 b (provided on the rear side) bythe transport thin-film member 21 b which is formed with the cuts 21 c.The developer is then transported into the developer transport room 11by the portion having the auxiliary thin-film 23.

The second developer transport member 22 transports the developer towardthe first developer transport member 21. A third developer transportmember (developer supply member) 24 and a fourth developer transportmember (developer supply member) 26 which are disposed in the seconddeveloper supply room 18 transport the developer in the second developersupply room 18 toward the developer drop passages 17.

The developer transport room 11, the first developer supply room 16, andthe second developer supply room 18 constitute a developer supplycontainer (11+16+18) according to the first embodiment.

The photoreceptor body cleaner CLk is disposed on the right of thesecond developer supply room 18. The photoreceptor body cleaner CLk hasa plate-like developer cleaning member (what is called a cleaning blade)31 which is in contact with the surface of the photoreceptor body Pk anda collection developer transport member 33 for transporting, to acollection developer containing room 32, developer that has been scrapedoff by the cleaning blade 31.

As shown in FIG. 3B, the visible image forming device UK is providedwith a film seal FS as an exemplary partition member/opening blockingmember. An external end portion of the film seal FS is guided outsidevia a through-hole (not shown) formed in the visible image formingdevice UK and its internal end portion is divided into two parts. Onepart is stuck to the bottom surface of the boundary portion of theopening 9 a in a state that the developer damming member 10 is locatedat the contained position, that is, the rotation shafts 10 b are fittedin the damming member support holes 9 b and the damming member main body10 a is in contact with the bottom surfaces of contained positionrestriction members 9 c. As shown in FIG. 4, the other part of theinternal end portion of the film seal FS is stuck to the wall so as toclose the developer supply mouth 11 a of the developer transport room11.

Therefore, the opening 9 a is closed and the initial developercontaining room 9 is sealed by the film seal FS. Furthermore, sealing ismade between the developer transport room 11 and the developercontaining room (2-4).

In the first embodiment, a two-component developer (what is called aninitial developer) in which a toner and a carrier are mixed together inadvance at a preset, prescribed ratio is contained in the sealed initialdeveloper containing room 9 and a toner as a supply developer iscontained in the developer supply container (11+16+18). The developercontaining room (2-4) is kept in a state that no developer exists there.Therefore, in a state that the film seal FS is attached, not only doesno developer exist in the developer containing room (2-4) but also it issealed. This prevents leakage of developer during transport or storagein a warehouse. The film seal FS is removed from the visible imageforming device UK before the visible image forming device UK is attachedto the image forming apparatus main body U1, whereupon the developerflows into the developer containing room (2-4) from the initialdeveloper containing room 9 and supply of a developer from the developersupply container (11+16+18) is enabled.

The members etc. that are given symbols 1-26 and FS constitute thedeveloper transport device according to the first embodiment.

Workings of Embodiment 1

In the printer U which has the above constituent features and is anexemplary image forming apparatus according to the first embodiment,when the visible image forming device UK is replaced, the film seal FSof a new visible image forming device UK is removed, whereupon thedeveloper that has been sealed in the initial developer transport room 9flows into the second agitation transport room 4 of the developercontaining room (2-4). At this time, the developer damming member 10 isswung from the contained position to the damming position about thecenter line of the rotation shafts 10 b.

The developer in the second agitation transport room 4 is transported bythe agitation transport member 8 while being agitated by it. Thedeveloper is transported past the developer damming member 10 which islocated at the position that is close to the downstream end in thedeveloper transport direction.

At this time, since the transport passage for the developer in thesecond agitation transport room 4 is narrowed by the developer dammingmember 10, the upper portion of the developer is stopped by thedeveloper damming member 10 and the developer is transported downstreamat a rate corresponding to the cross section of the second agitationtransport member 8 which is located under the developer damming member10. The developer that is dammed up by the developer damming member 10is agitated in such a manner as to form a local circulation togetherwith developer that comes additionally in the wedge-shaped region formedbetween the developer damming member 10 and the second agitationtransport member 8. In particular, lumps of cohered toner that have notsufficiently been reduced in size as they are transported along thesecond agitation transport room 4 are larger than toner that has beenbroken up sufficiently, and hence tend to go up as they are transportedalong the second agitation transport room 4. Therefore, they are dammedup effectively at the position of the developer damming member 10 andbroken up through agitation.

The developer that has been agitated sufficiently by the developerdamming member 10 is transported by the second agitation transportmember 8, passes through the first agitation transport room 3., and issupplied to the developing roll G1 k. Developer that has not been usedfor the development is again transported to the second agitationtransport room 4 (circulatory transport).

As the toner is consumed by developments, additional toner is suppliedfrom the developer supply container (11+16+18), transported and agitatedby the second agitation transport member 8, further agitated by thedeveloper damming member 10 which is located at the downstream position,and finally supplied to the developing roll G1 k.

(Example)

FIG. 8 is a graph in which the horizontal axis represents the timeelapsed from the start of toner supply and the vertical axis representsthe toner density, and illustrates an experiment of the firstembodiment.

An experiment is conducted to check the effect of the developer dammingmember 10 according to the first embodiment. In the experiment, in theconfiguration according to the first embodiment, how the toner densitydetected by the toner density sensor SN2 varies depending on thepresence/absence of the developer damming member 10 is measured when aset of toner supply of 0.5 sec and supply suspension of 0.5 sec isrepeated ten times consecutively. FIG. 8 shows a result of theexperiment.

As shown in FIG. 8, when a developer that has been supplied by anoperation that a set of toner supply of 0.5 sec and supply suspension of0.5 sec is repeated ten times, that is, a supply operation of(0.5+0.5)×10=10 sec, has been transported by the second agitationtransport member 8 and reaches the position of the toner density sensorSN2, large toner density values are detected during a first detectionperiod t1. The developer is further transported along the firstagitation transport room 3 and the second agitation transport room 4 inthis order and again reaches the position of the toner density sensorSN2 after making a first circulation. As a result, large toner densityvalues are detected again during a second detection period t2. In thismanner, the developer is detected during a third detection period t3, afourth detection period t4, . . . as it makes a second circulation, athird circulation, . . . .

The developer which is transported and circulated by the agitationtransport members 7 and 8 is spread gradually as it is transported,whereby a high-toner-density portion becomes less likely to occur. Asshown in FIG. 8, the peak toner density lowers gradually. In a statethat the toner density exhibits a high peak, that is, the developer hasnot been spread much, the toner density of the developer that issupplied from the first agitation transport room 3 to the developingroll G1 y, G1 m, G1 c, or G1 k varies, as a result of which an imageproduced may have a deep color band or streak or, in the worst case,small lumps of toner that have not been broken up. If a process controlis performed in a state that the toner density is varying, the densityof a patch image also varies to lower the accuracy. Where the developerdamming member 10 is provided, cohered toner is broken up throughagitation and peaks of the toner density converge earlier, whereby theaccuracy of a process control is increased.

Embodiment 2

FIGS. 9A and 9B illustrate a developer damming member according to asecond exemplary embodiment of the invention. FIGS. 9A and 9B are afront view and a side view corresponding to FIGS. 7A and 7B of the firstembodiment, respectively.

Next, an image forming apparatus having the developer damming memberaccording to the second embodiment of the invention will be described.In the description of the second embodiment, components havingcorresponding components in the first embodiment will be given the samereference symbols as the latter and will not be described in detail. Thesecond embodiment is different from the first embodiment only in thefollowing points.

As shown in FIGS. 9A and 9B, in the developer damming member 10′according to the second embodiment, a top portion of an agitation membersurrounding portion 10 c is formed with three passage grooves 10 d.

Workings of Embodiment 2

In the image forming apparatus U according to the second embodimenthaving the above configuration, developer that has been transported tothe position of the developer damming member 10′ and has been dammed upby it is agitated because of being dammed up. Furthermore, the developeris pressed by developer coming additionally and is crushed by thepassage grooves 10 d in passing through them. In this manner, thedeveloper is transported downstream after being broken up. Developerthat has been agitated by the local circulation is further broken up dueto a more turbulent flow. As such, the image forming apparatus Uaccording to the second embodiment provides the same advantages as theimage forming apparatus according to the first embodiment.

Embodiment 3

FIGS. 10A and 10B illustrate a developer damming member according to athird exemplary embodiment of the invention. FIGS. 10A and 10B are aside view and a front view corresponding to FIGS. 5A and 7A of the firstembodiment, respectively.

Next, an image forming apparatus having the developer damming memberaccording to the third embodiment of the invention will be described. Inthe description of the third embodiment, components having correspondingcomponents in the first embodiment will be given the same referencesymbols as the latter and will not be described in detail. The thirdembodiment is different from the first embodiment only in the followingpoints.

As shown in FIG. 10, the developer damming member 10″ according to thethird embodiment has slide support receiving portions 10 b″ as exemplarysupport receiving portions instead of the rotation shafts 10 b. Aninitial developer containing room 9″ is configured correspondingly; thatis, the damming member support holes 9 b and the contained positionrestriction members 9 c are omitted and, instead, a pair of (right andleft) groove-shaped slide support portions 9 b″ as exemplary dammingmember support portions for supporting the respective slide supportreceiving portions 10 b″ are formed. Therefore, the developer dammingmember 10″ can move slidingly from a contained position (not shown)where it is contained in the initial developer containing room 9″ to adamming position shown in FIG. 10. That is, the developer damming member10″ is supported slidably.

Workings of Embodiment 3

In the image forming apparatus U according to the third embodimenthaving the above configuration, when the film seal FS has been removed,the developer damming member 10″ is moved slidingly from the containedposition to the damming position. Developer that has been transported tothe developer damming member 10″ which is located at the dammingposition is dammed up by the developer damming member 10″ and agitatedthere. Furthermore, in the image forming apparatus U according to thethird embodiment, even if receiving force from the developer, thedeveloper damming member 10″ that has been moved to the damming positioneffectively dams up and agitates the developer passing the position ofthe developer stop member 10″ while being held at the stop positionreliably. As such, the image forming apparatus U according to the thirdembodiment provides the same advantages as the image forming apparatusaccording to the first embodiment.

(Modifications)

The embodiments of the invention have been described above. However, theinvention is not limited to the embodiments and various modificationsare possible without departing from the spirit and scope of theinvention described in the claims. Exemplary modifications H01-H08 ofthe invention will be described below.

(H01) The above embodiments are directed to the printers as exemplaryimage forming apparatus. However, the invention is not limited toprinters and can be applied to facsimile machines, copiers, etc. as wellas multi-function machines having all or part of those functions.Furthermore, the invention is not limited to multi-color-developmenttype image forming apparatus and can be applied to single-color(monochrome) image forming apparatus.

(H02) In the above embodiments, the developer damming member 10, 10′, or10″ is disposed in the second agitation transport room 4. However, thelocation of the developer damming member is not limited to the aboveposition and it may be disposed at an arbitrary possible positionaccording to the design. Plural developer damming members may bedisposed in the second agitation transport room 4.

(H03) In the above embodiments, the developing device G and thedeveloper supply container (11+16+18) are integrated with each other soas to be replaced together. However, the invention is not limited tosuch a configuration. A configuration is possible in which thedeveloping device and the developer supply container are separated fromeach other and connected to each other by a developer transport memberand developer is transported from the former to the latter.

(H04) In the second embodiment, the grooves 10 d may be modified so asto have an arbitrary shape.

(H05) In the above embodiments, if the angle θ formed by the developerdamming member 10 and the rotary shaft 8 a of the agitation transportmember 8 is set at an obtuse angle, the dammed developer tends to stayover the developer damming member 10 and is rendered stagnant.Therefore, it is desirable that the angle θ be set at an acute angle.However, it is possible to set it at an obtuse angle.

(H06) In the above embodiments, it is desirable to provide the agitationmember surrounding portion 10 c. However, it may be omitted.

(H07) In the above embodiments, each developer transport member is anauger having a rotary shaft and a spiral transport blade. However, thestructure of each developer transport member is not limited to it.Developer transport members having arbitrary shapes may be used such asa developer transport member having a helical spring shape (coil springshape) and a developer transport member in which semicircular transportblades are supported obliquely by a rotary shaft.

(H08) In the above embodiments, a developer which is a two-componentdeveloper containing a toner and a carrier is contained in the initialdeveloper containing room 9 and only a toner is contained in thedeveloper supply container (11+16+18). However, the invention is notlimited to this configuration. A configuration is possible in whichdeteriorated developer is ejected little by little from each developingdevice and a high-density developer containing a carrier and a tonerthat is higher in density than the toner in each developing device issupplied to each developing device. Furthermore, the developer is notlimited to the two-component developer and the invention can be appliedto an image forming apparatus which uses a one-component developer.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theexemplary embodiments were chosen and described in order to best explainthe principles of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A developer transport device comprising: a developer containing roomfor containing a developer; a developer transport member disposed in thedeveloper containing room, the developer transport member transportingthe developer in a developer transport direction; and a developerdamming member disposed in the developer containing room over thedeveloper transport member, the developer damming member damming up thedeveloper located above the developer transport member.
 2. The developertransport device according to claim 1, wherein the developer transportmember rotates; and the developer damming member is shaped so as tosurround a part of an outer circumference of a rotation locus of thedeveloper transport member.
 3. The developer transport device accordingto claim 1, wherein the developer damming member is inclined so as tocome closer to the developer transport member as a position in thedeveloper containing room goes downstream in the developer transportdirection.
 4. The developer transport device according to claim 1,further comprising: an initial developer containing room disposed abovethe developer containing room, for containing a developer; and partitionmember that separates the initial developer containing room and thedeveloper containing room from each other, the partition member beingremovable, wherein the developer damming member is movable between acontained position where the developer damming member is containedinside the initial developer containing room and a damming positionwhere the developer damming member is located in the developercontaining room and dams up the developer; and the developer dammingmember is held at the contained position when the partition member isattached, and the developer flows from the initial developer containingroom into the developer containing room and the developer damming membermoves to the damming position when the partition member is removed. 5.The developer transport device according to claim 4, wherein thedeveloper damming member is capable of swinging between the containedposition and the damming position.
 6. The developer transport deviceaccording to claim 4, wherein the developer damming member is capable ofsliding between the contained position and the damming position.
 7. Thedeveloper transport device according to claim 1, wherein the developerdamming member is disposed at a position between a downstream end of adeveloper supply mouth through which a developer is supplied to thedeveloper containing room and a developer holding body.
 8. The developertransport device according to claim 1, the developer damming member hasa passage groove through which a part of the developer passes.
 9. Adeveloping device characterized by comprising: a developer containingroom for containing a developer; a developer transport member disposedin the developer containing room, the developer transport membertransporting the developer in a developer transport direction; adeveloper damming member disposed in the developer containing room overthe developer transport member, the developer damming member damming upthe developer located above the developer transport member; and adeveloper holding body that develops a latent image into a visible imagewith the developer transported.
 10. A visible image forming devicecomprising: an image holding body; and a developing device comprising: adeveloper containing room opposed to a development region, forcontaining a developer; a developer transport member disposed in thedeveloper containing room, the developer transport member transportingthe developer in a developer transport direction; a developer dammingmember disposed in the developer containing room over the developertransport member, the developer damming member damming up the developerlocated above the developer transport member; and a developer holdingbody that develops a latent image into a visible image with thedeveloper transported.
 11. An image forming apparatus comprising: animage holding body; a developing device comprising: a developercontaining room opposed to a development region, for containing adeveloper, a developer transport member disposed in the developercontaining room, the developer transport member transporting thedeveloper in a developer transport direction, a developer damming memberdisposed in the developer containing room over the developer transportmember, the developer damming member damming up the developer locatedabove the developer transport member, and a developer holding body thatdevelops a latent image into a visible image with the developertransported; and a transfer device that transfers the visible image onthe image holding body to a transfer member.
 12. A developer transportdevice comprising: a developer containing room for containing adeveloper; a developer transport member disposed in the developercontaining room, the developer transport member transporting thedeveloper in a developer transport direction; and a developer dammingmember that overhangs the developer transport member so as to narrow atransport passage of the developer being transported and dams up a partof the developer.